1. Field
This disclosure relates generally to methods of making semiconductor devices, and more specifically, to a process for making a semiconductor device using partial etching.
2. Related Art
High speed semiconductor devices require higher gate capacitance. Higher gate capacitance has been achieved in semiconductor devices with silicon-oxide gate dielectric layers by thinning the gate dielectric layer. Thinner gate dielectric layer, however, results in leakage across the thin dielectric layer. To address this problem, increasingly, semiconductor devices have high-k dielectric layers, which can have sufficient thickness to reduce gate leakage and yet maintain sufficiently high gate capacitance.
In fabricating dual metal gate devices, typically the first metal layer is covered with a hard mask layer, patterned, and etched down to the gate dielectric layer. Next, the photo resist and the hard mask layer are removed and a second metal layer is deposited. When the hard mask layer is removed, however, the removal of the hard mask layer can damage the gate dielectric layer. In particular, the exposure of the gate dielectric layer to the removal chemistry used for removing the hard mask layer can damage the gate dielectric layer. Similarly, the removal of photo resist can damage any exposed dielectric layer or any exposed metal layer.
Accordingly, there is a need for a process for making a semiconductor device using partial etching.